Calculations with Equations CHAPTER 9 Mole Ratios Calculations with Equations

Mole-Mole Factor Shows the mole-to-mole ratio between two of the substances in a balanced equation Derived from the coefficients of any two substances in the equation

Writing Mole Factors – identifies the mole-ratio existing between the substances involved in a given chemical equation 4 Fe + 3 O2 2 Fe2O3 Fe and O2 4 mol Fe and 3 mol O2 3 mol O2 4 mol Fe Fe and Fe2O3 4 mol Fe and 2 mol Fe2O3 2 mol Fe2O3 4 mol Fe

4 Fe + 3 O2 2 Fe2O3 MOLE RATIO of O2 and Fe2O3 3 mol O2 and 2 mol Fe2O3 2 mol Fe2O3 3 mol O2

Review examples 3 H2(g) + N2(g) 2 NH3(g) A. A mol factor for H2 and N2 is 1) 3 mol N2 2) 1 mol N2 3) 1 mol N2 1 mol H2 3 mol H2 2 mol H2 B. A mol factor for NH3 and H2 is 1) 1 mol H2 2) 2 mol NH3 3) 3 mol N2 2 mol NH3 3 mol H2 2 mol NH3

Chemical Calculations 4 Fe + 3 O2 2 Fe2O3 How many moles of Fe2O3 are produced when 6.0 moles O2 react? 6.0 mol O2 x mol Fe2O3 = 4.0 mol Fe2O3 mol O2 2 3

How many moles of Fe are needed to react with 12.0 mol of O2? 4 Fe + 3 O2 2 Fe2O3 12.0 mol O2 x mol Fe = 16.0 mol Fe mol O2 4 3

4 Fe + 3 O2 2 Fe2O3. How many grams of O2 are needed to produce 0 4 Fe + 3 O2 2 Fe2O3 How many grams of O2 are needed to produce 0.400 mol of Fe2O3? 0.400 mol Fe2O3 x 3 mol O2 x 32.0 g O2 2 mol Fe2O3 1 mol O2 = 19.2 g O2

Calculating Mass of A Substance in a Stoichiometric Equation Balance equation Convert starting amount to moles Use coefficients to write a mol-mol factor Convert moles of desired to grams

Calculation The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? Write the equation H2 (g) + O2 (g) H2O (g) Balance the equation 2 H2 (g) + O2 (g) 2 H2O (g)

Organize data mol bridge 2 H2 (g) + O2 (g) 2 H2O (g) ? g 13.1 g Plan g H2O mol H2O mol O2 g O2 Setup 13.1 g H2O x 1 mol H2O x 1 mol O2 x 32.0 g O2 18.0 g H2O 2 mol H2O 1 mol O2 = 11.6 g O2

How many O2 molecules will react with 505 grams of Na to form Na2O? 4 Na + O2 2 Na2O 505 g Na x 1 mol Na x 1 mol O2 x 6.02 x 1023 23.0 g Na 4 mol Na 1 mol O2 = 3.30 x 1024 molecules

Acetylene gas C2H2 burns in the oxyactylene torch for welding Acetylene gas C2H2 burns in the oxyactylene torch for welding. How many grams of C2H2 are burned if the reaction produces 75.0 g of CO2? 2 C2H2 + 5 O2 4 CO2 + 2 H2O 75.0 g CO2 x 1 mol CO2 x 2 mol C2H2 x 26.0 g C2H2 44.0 g CO2 4 mol CO2 1 mol C2H2 = 22.2 g C2H2